Interface arbitration for a wired tag

ABSTRACT

Various exemplary embodiments relate to an integrated circuit (IC) including: a memory; a radio frequency (RF) interface configured to access the memory; a wired interface connected to a host and configured to access the memory; and an arbitration module configured to prevent concurrent access to the memory by more than one interface. Various exemplary embodiments relate to a method of controlling access in a dual interface tag having a wired interface and a radio frequency (RF) interface operable in an idle state, a wired lock state, and a RF locked state.

TECHNICAL FIELD

Various exemplary embodiments disclosed herein relate generally tocontactless cards and contactless tags.

BACKGROUND

Contactless tags are used in identification products such as smart cardsand Radio Frequency Identification (RFID) tags for a variety ofpurposes. International standard ISO14443A is the industry standard forcontactless smart cards. ISO14443A compliant products provide RFcommunication technology for transmitting data between a card or tag anda reader device.

Near Field Communication (NFC) is a very short-range wireless technologyfor distances measured in centimeters. NFC is optimized for intuitive,easy and secure communications between various devices without userconfiguration. NFC is compatible with contactless smart card platforms.NFC devices can operate like a contactless smart card, making themcompatible with ISO14443A compliant systems. Such functionality iscalled card emulation.

The NFC Forum is a non-profit industry association advancing the use ofNFC short-range wireless interaction in a variety of devices. The NFCForum provides a number of technical specifications defining theoperation of NFC devices. The NFC Forum has defined specifications forcontactless cards called NFC Forum tags.

SUMMARY

A brief summary of various exemplary embodiments is presented. Somesimplifications and omissions may be made in the following summary,which is intended to highlight and introduce some aspects of the variousexemplary embodiments, but not to limit the scope of the invention.Detailed descriptions of a preferred exemplary embodiment adequate toallow those of ordinary skill in the art to make and use the inventiveconcepts will follow in later sections.

Various exemplary embodiments relate to an integrated circuit (IC)including: a memory; a radio frequency (RF) interface configured toaccess the memory; a wired interface connected to a host and configuredto access the memory; and an arbitration module configured to preventconcurrent access to the memory by more than one interface

In various embodiments the IC of further includes a field detection (FD)pin that indicates whether an RF field is present.

In various embodiments, the arbitration module comprises: a firstregister configured to indicate the status of the RF interface and asecond register configured to indicate the status of the wiredinterface.

In various embodiments, the arbitration module is configured to blockcommunication via the wired interface if the first register indicatesthat the RF interface is active and to block communication via the RFinterface if the second register indicates that the wired interface isactive.

In various embodiments, the arbitration module is configured to set thefirst register when the FD pin indicates that an RF field is present.

In various embodiments, the arbitration module waits until the secondregister indicates that the wired interface is inactive before blockingthe wired interface.

In various embodiments, the arbitration module is configured to resetthe first register when the field detection pin indicates that no RFfield is present.

In various embodiments, the arbitration module is configured to controlthe first register based on commands received via the RF interface.

In various embodiments, the arbitration module is configured to controlthe second register based on an address received via the wiredinterface.

In various embodiments, the arbitration module is configured to controlthe second register based on commands received via the wired interface.

In various embodiments, the wired interface is a integratedinter-circuit (I²C) interface.

Various exemplary embodiments relate to a method of controlling accessin a dual interface tag having a wired interface and a radio frequency(RF) interface operable in an idle state, a wired lock state, and a RFlocked state. The method includes: transitioning from an idle state to awired lock state based on a first command received via the wiredinterface; transitioning from a wired lock state to an idle state basedon a second command received via the wired interface or a lack of poweron the wired interface; transitioning from an idle state to an RF lockedstate based on a status of the RF interface; and transitioning from anRF locked state to an idle state based on a status of the RF interface.

In various embodiments, the method further includes transitioning from awired lock state to an RF locked state based on detection of an RFfield.

In various embodiments, the status of the RF interface is based on thepresence of an RF field.

In various embodiments, the status of the RF interface is based oncommands received via the RF interface.

In various embodiments, the step of transitioning from an idle state toan RF locked state based on a status of the RF interface comprisessetting a register associated with the RF interface based on thepresence of a RF field.

In various embodiments, the step of transitioning from an idle state toa wired lock state based on a first command received via the wiredinterface includes: receiving an address via the wired interface;determining that the address is a slave address of the tag on the wiredinterface; and setting a register associated with the wired interface toindicate that the wired interface is busy.

In various embodiments, the step of transitioning from an RF lockedstate to an idle state is based on a status of the RF interfaceincludes: receiving a HALT message via the RF interface; and resetting aregister associated with the RF interface to indicate that the RFinterface is not busy.

It should be apparent that, in this manner, various exemplaryembodiments enable a dual interface tag and method of controlling accessto the dual interface tag. In particular, by locking access to the firstinterface that attempts to access the tag, an arbitration module mayenable access via at least two interfaces and prevent corruption of datastored on the tag.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand various exemplary embodiments, referenceis made to the accompanying drawings, wherein:

FIG. 1 illustrates an exemplary environment for a dual interface tag;

FIG. 2 illustrates an exemplary dual interface tag;

FIG. 3 illustrates a state diagram showing various states of the dualinterface tag in a first arbitration mode; and

FIG. 4 illustrates a state diagram showing various states of the dualinterface tag in a second arbitration mode.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to likecomponents or steps, there are disclosed broad aspects of variousexemplary embodiments.

FIG. 1 illustrates an exemplary environment for a dual interface tag110. Tag 110 may be a contactless tag that also includes a wiredinterface. Tag 110 may be in communication with NFC device 120 and host130. Tag 110 may communicate with one or more NFC devices 120 via awireless link such as, for example, RF signals. Tag 110 may communicatewith host 130 via a wired interface. Accordingly, tag 110 may bephysically connected to host 130. Tag 110 may be embedded within host130 or attached to a surface of host 130. Tag 110 may also be removablyconnected to host 130, such as, for example, by plugging into a port ofhost 130.

Tag 110 may be an integrated circuit that stores information in aninternal memory 112 that can be read by an external device such as NFCdevice 120. Tag 110 may be compliant with NFC Forum specifications forNFC Forum tags. Accordingly, tag 110 may receive and process a commonset of commands used by NFC Forum tags. Tag 110 may also be read by host130. Tag 110 may include memory 112, RF interface 114, wired interface116, and field detection pin 118. Tag 110 may lack an internal powersource and be powered by an external interface. For example, tag 110 mayreceive power via the RF interface 114 as a passive RFID tag and alsoreceive power via a wired interface 116.

Memory 112 may include volatile memory and/or non-volatile memory. Invarious exemplary embodiments, memory 112 includes a non-volatileelectronically erasable programmable read only memory (EEPROM). AnEEPROM may continue to store data when tag 110 is no longer powered.Memory 112 may be arranged in a plurality of blocks having a fixednumber of bytes. In various exemplary embodiments, memory 112 isarranged according to one of the NFC Forum tag specifications.

RF interface 114 may include hardware for transmitting and receivingdata via radio frequency signals. Accordingly, RF interface 114 mayinclude an antenna, transmitter, receiver, and/or transceiver. RFinterface 114 may be compliant with the NFC Forum specifications andoperate accordingly. RF interface 114 may be used by NFC device 120 toread and/or write data to memory 112.

Wired interface 116 may include one or more wires connecting NFC tag 110to host 130. In various exemplary embodiments, wired interface 116 maybe an inter-integrated circuit (I²C) interface. Such a wired interfacewill be described in further detail below. Any other wired interface forcommunicating data may also be used. Wired interface 116 may be assigneda slave address for NFC tag 110. Wired interface 116 may be used by host112 to read and/or write data to memory 112.

Field detection (FD) pin 118 may be an output pin of tag 110. FD pin 118may indicate whether tag 110 is currently busy on RF interface 114. FDpin 118 may be connected to host 130. In various embodiments, FD pin 118may be used to provide a trigger signal that causes an interrupt on host130. Such a trigger signal may indicate that data is available forreading on tag 110. FD pin 118 may also allow host 130 to know when tag110 is available for reading and/or writing via wired interface 116.

NFC device 120 may be any device capable of communicating with tag 110via RF interface 114. In various exemplary embodiments, NFC device 120may communicate with tag 110 as defined by NFC Forum specifications. NFCdevice 120 may be a cell phone, mobile phone, smart phone, tabletcomputer, PDA, or any other computing device.

RF interface 122 may include hardware for transmitting and receivingdata via radio frequency signals. Accordingly, RF interface 122 mayinclude an antenna, transmitter, receiver, and/or transceiver. RFinterface 122 may be compliant with the NFC Forum specifications andoperate accordingly. RF interface 122 may be used by NFC device 120 toread and/or write data to memory 112.

Host 130 may be any device capable of communicating via a wiredinterface 116. Accordingly, host 130 may be a computing device such as acell phone, mobile phone, smart phone, tablet, laptop, or desktopcomputer, or any other computing device. Host 130 may also include otherelectronic devices. For example, host 130 may include a Bluetoothheadset, speakers, video player, or any other electronic device. Dualinterface tag 110 may be connected to host 130 and extend thefunctionality of host 130 for wireless communications such as NFC.

FIG. 2 illustrates an exemplary dual interface tag 110. Dual interfacetag 110 may include: RF interface 114, field detection pin 118, SDA pin220, SCL pin 222, VCC pin 224, EEPROM 112, arbitration module 230,I2C_IF_ON_OFF register 240, RF_IF_ON_OFF register 250, andRF_FIELD_PRESENCE_INDICATOR register 260.

SDA pin 220 may be a component of wired interface 116. For example, anSDA wire is defined for an I²C interface. SDA pin 220 may carry data andaddresses for wired interface 116.

SCL pin 222 may be a component of wired interface 116. For example, anSCL wire is defined for an I²C interface. SCL pin 222 may provide aclock signal for the wired interface 116. The clock signal may determinethe transmission speed of the wired interface 116.

VCC pin 224 may be a component of wired interface 116. VCC pin 224 mayprovide power to the tag 110. Accordingly, tag 110 may operate whenpowered solely via the wired interface 116.

Memory 112 may be an electronically erasable programmable read onlymemory (EEPROM). Memory 112 may be used by tag 110 to store data. Accessto memory 112 may be controlled. For example, memory 112 may be set to aRead-only state such that it cannot be erased or written. Access tomemory 112 may also be controlled by arbitration module 230 as discussedin further detail below.

Arbitration module 230 may include logic circuitry and/or instructionsexecutable by an arithmetic logic unit (ALU) or processor. Arbitrationmodule 230 may control access to tag 110. Arbitration module 230 mayprevent concurrent access to the memory 112 by more than one interface.Arbitration module 230 may determine which interface may access the tag110. Arbitration module 230 may transition tag 110 between variousaccess states. In an idle state, either interface may gain access to tag110. In an RF locked state, tag 110 may be locked to the RF interface114 and the wired interface 116 may be blocked from access. In a wiredlocked state, tag 110 may be accessed via wired interface 116 and RFinterface 114 may be blocked.

Arbitration mode indicator 235 may include a register, flag, or memoryconfigured to indicate an arbitration mode of tag 110. The arbitrationmode may determine how arbitration module 230 determines which interfacemay access tag 110 or how arbitration module 230 transitions betweenaccess states. In various exemplary embodiments, arbitration modeindicator 235 may be set during a test of tag 110. In variousalternative embodiments, arbitration mode indicator 235 may be set viaone or more interfaces.

I2C_IF_ON_OFF register 240 may be a register configured to indicatewhether wired interface 116 is in use. Register 240 may be set or resetby wired interface 116. Register 240 may be set when tag 110 isaddressed via wired interface 116. Register 240 may be reset when tag110 receives an invalid address via wired interface 116, when tag 110receives an instruction to reset register 240, or when wired interface116 loses power, that is, when VCC 224 is off.

RF_IF_ON_OFF register 250 may be a register configured to indicatewhether RF interface 114 is in use. Register 250 may be set or reset byRF interface 114. In a first arbitration mode, register 250 may be setaccording to FD pin 118. Register 250 may indicate that RF 114 is in usewhenever an RF field is detected by tag 110. In a second arbitrationmode, register 250 may be set or reset by commands from RF interface114. Register 250 may be set when tag 110 receives a valid command viathe RF interface 114. Register 250 may be reset when tag 110 is set to aHALT state via a HALT command received via the RF interface 114 or whentag 110 has an RF power on reset due to lack of an RF field.

RF_FIELD_PRESENCE_INDICATOR 260 may be a register configured to indicatethe status of FD pin 118. Register 260 may provide a convenient accesspoint to determine the status of the FD pin 118. For example, if host130 is not connected to FD pin 118, host 130 may read the status ofregister 260 via wired interface 116.

FIG. 3 illustrates a state diagram showing various exemplary states fortag 110 in a first arbitration mode. Tag 110 may start in an idle state310. In the idle state 310 both interfaces 114 and 116 may be inactive.Registers 240, 250, and 260 may all be set to 0, indicating that therespective interfaces are inactive. Tag 110 may be accessible towhichever interface is first to attempt to access tag 110.

Tag 110 may transition from idle state 310 to RF locked state 320 viatransition path 312. Transition path 312 may occur when tag 110 detectsan RF field. FD pin 118 may turn on indicating an RF field is present.RF_IF_ON_OFF register 250 may automatically be set to 1, indicating theRF interface 114 is now busy. In RF locked state 320, RF interface 114may be able to access resources of tag 110. For example, an NFC device120 may be able to read memory 112. Wired interface 116 may be blockedfrom access. Tag 110 may ignore any communications received via wiredinterface 116.

Tag 110 may transition from RF locked state 320 to idle state 310 viatransition path 322. Transition path 322 may occur when tag 110 leavesthe RF field or the RF field is turned off. In either case, tag 110 mayno longer detect an RF field and FD pin 118 may be off. RF_IF_ON_OFFregister 250 may automatically be set to 0, indicating that the RFinterface 114 is not busy.

Tag 110 may transition from idle state 310 to wired locked state 330 viatransition path 314. Transition path 314 may occur when tag 110 receivesa command via wired interface 116. For example, wired interface 116 maybe addressed according to its slave address on an I²C interface.Arbitration module 230 may set I2C_IF_ON_OFF interface 240 to 1,indicating that the wired interface 116 is busy.

In wired locked state 330, the resources of tag 110 may be accessiblevia the wired interface 116. For example, a host 130 may send commandsto read or write memory 112. The host 130 may also be able to write toI2C_IF_ON_OFF register 240. RF interface 114 may be blocked fromaccessing tag 110. Tag 110 may not respond to an RF signal when it is inwired locked state 330.

Tag 110 may transition from wired locked state 330 to idle state 310 viatransition path 332. Transition path 332 may occur when tag 110 receivesa command to reset I2C_IF_ON_OFF register 240. For example, host 130 maysend a command to write a 0 to I2C_IF_ON_OFF register 240.Alternatively, I2C_IF_ON_OFF register 240 may be reset when tag 110receives an invalid address on wired interface. For example, a differentnode is addressed via wired interface 116. Another possible way to resetI2C_IF_ON_OFF register 240 is when wired interface 116 loses power. Thatis, when VCC pin 224 turns off, I2C_IF_ON_OFF register 240 may be set to0 automatically, or by arbitration module 230.

Tag 110 may transition from wired locked state 320 directly to RF lockedstate 320 via transition path 334. Transition path 334 may occur whentag 110 detects an RF field while in wired locked state 330. FD pin 118may indicate that an RF field is present, and RF_IF_ON_OFF register 250may automatically be set to 1. Tag 110 may temporarily indicate that itis busy on both the wired interface 116 and RF interface 114.Arbitration module 230 may reset the I2C_IF_ON_OFF register 240 to 0based on the detected RF field. In various embodiments, tag 110 mayremain in wired locked state 330 until a most recent command receivedvia wired interface 116 is completed, then follow transition path 334.

FIG. 4 illustrates a state diagram showing various exemplary states fortag 110 in a second arbitration mode. The states 410, 420, and 430 mayrespectively correspond to states 310, 320 and 330 discussed aboveregarding FIG. 3. Transition paths 414 and 432 may be similar totransition paths 314 and 332, respectively. The second arbitration modemay include no equivalent to transition path 334. In other words, thesecond arbitration mode may provide no transition between a wired lockedstate 430 and an RF locked state 420. Instead, tag 110 may changeinterfaces only by returning to the idle state.

Tag 110 may transition from idle state 410 to RF locked state 420 viatransition path 412. Transition path 412 may occur when tag 110 receivesa valid command via RF interface 114. For example, tag 110 may receive apolling command, read command, or write command from an NFC device 120.Arbitration module 230 may set RF_IF_ON_OFF register 250 to 1,indicating that the RF interface 114 is busy.

Tag 110 may transition from RF locked state 420 to idle state 410 viatransition path 422. Transition path 422 may occur when tag 110 receivesa command via RF interface 110. Specifically, tag 110 may receive a HALTcommand. Arbitration module 230 may reset the RF_IF_ON_OFF register 250to 0, indicating the RF interface 114 is no longer busy. Alternatively,similar to the first arbitration mode, transition path 422 may alsooccur when tag 110 is removed from the RF field or the RF field isturned off. FD pin 118 may turn off and arbitration module 230 may resetRF_IF_ON_OFF register 250 to 0.

Tag 110 may transition from idle state 410 to wired lock state 430 viatransition path 414. Transition path 414 may be identical to transitionpath 314 described above.

Tag 110 may transition from wired lock state 430 to idle state 410 viatransition path 432. Transition path 432 may be identical to thetransition path 332 described above.

According to the foregoing, various exemplary embodiments provide a dualinterface tag and method of controlling access to the dual interfacetag. In particular, by locking access to the first interface thatattempts to access the tag, an arbitration module may enable access viaat least two interfaces and prevent corruption of data stored on thetag.

It should be apparent from the foregoing description that portions ofvarious exemplary embodiments of the invention may be implemented inhardware and/or firmware. Furthermore, various exemplary embodiments maybe implemented as instructions stored on a machine-readable storagemedium, which may be read and executed by at least one processor toperform the operations described in detail herein. A machine-readablestorage medium may include any mechanism for storing information in aform readable by a machine, such as a personal or laptop computer, aserver, or other computing device. Thus, a machine-readable storagemedium may include read-only memory (ROM), random-access memory (RAM),magnetic disk storage media, optical storage media, flash-memorydevices, and similar storage media.

It should be appreciated by those skilled in the art that any blockdiagrams herein represent conceptual views of illustrative circuitryembodying the principals of the invention. Similarly, it will beappreciated that any flow charts, flow diagrams, state transitiondiagrams, pseudo code, and the like represent various processes whichmay be substantially represented in machine readable media and soexecuted by a computer or processor , whether or not such computer orprocessor is explicitly shown.

Although the various exemplary embodiments have been described in detailwith particular reference to certain exemplary aspects thereof, itshould be understood that the invention is capable of other embodimentsand its details are capable of modifications in various obviousrespects. As is readily apparent to those skilled in the art, variationsand modifications can be affected while remaining within the spirit andscope of the invention. Accordingly, the foregoing disclosure,description, and figures are for illustrative purposes only and do notin any way limit the invention, which is defined only by the claims.

What is claimed is:
 1. An integrated circuit (IC) comprising: a memory;a radio frequency (RF) interface configured to access the memory; awired interface connected to a host and configured to access the memory;and an arbitration module configured to prevent concurrent access to thememory by more than one interface.
 2. The IC of claim 1, furthercomprising a field detection (FD) pin that indicates whether an RF fieldis present.
 3. The IC of claim 1, wherein the arbitration modulecomprises: a first register configured to indicate the status of the RFinterface and a second register configured to indicate the status of thewired interface.
 4. The IC of claim 3, wherein the arbitration module isconfigured to block communication via the wired interface if the firstregister indicates that the RF interface is active and to blockcommunication via the RF interface if the second register indicates thatthe wired interface is active.
 5. The IC of claim 3, further comprisinga field detection (FD) pin that indicates whether an RF field is presentwherein the arbitration module is configured to set the first registerwhen the FD pin indicates that an RF field is present.
 6. The IC ofclaim 5, wherein the arbitration module waits until the second registerindicates that the wired interface is inactive before blocking the wiredinterface.
 7. The IC of claim 3, wherein the arbitration module isconfigured to reset the first register when the FD pin indicates that noRF field is present.
 8. The IC of claim 3, wherein the arbitrationmodule is configured to control the first register based on commandsreceived via the RF interface.
 9. The IC of claim 3, wherein thearbitration module is configured to control the second register based onan address received via the wired interface.
 10. The IC of claim 3,wherein the arbitration module is configured to control the secondregister based on commands received via the wired interface.
 11. The ICof claim 1, wherein the wired interface is an integrated inter-circuit(I²C) interface.
 12. A method of controlling access in a dual interfacetag having a wired interface and a radio frequency (RF) interfaceoperable in an idle state, a wired lock state, and a RF locked state,the method comprising: transitioning from an idle state to a wired lockstate based on a first communication received via the wired interface;transitioning from a wired lock state to an idle state based on a secondcommunication received via the wired interface or a lack of power on thewired interface; transitioning from an idle state to an RF locked statebased on a status of the RF interface; and transitioning from an RFlocked state to an idle state based on a status of the RF interface. 13.The method of claim 12 further comprising transitioning from a wiredlock state to an RF locked state based on detection of an RF field. 14.The method of claim 12, wherein the status of the RF interface is basedon the presence of an RF field.
 15. The method of claim 12, wherein thestatus of the RF interface is based on commands received via the RFinterface.
 16. The method of claim 10, wherein the step of transitioningfrom an idle state to an RF locked state based on a status of the RFinterface comprises setting a register associated with the RF interfacebased on the presence of a RF field.
 17. The method of claim 12, whereinthe step of transitioning from an idle state to a wired lock state basedon a first communication received via the wired interface comprises:receiving an address via the wired interface; determining that theaddress is a slave address of the tag on the wired interface; andsetting a register associated with the wired interface to indicate thatthe wired interface is busy.
 18. The method of claim 12, wherein thestep of transitioning from an RF locked state to an idle state based ona status of the RF interface comprises: receiving a HALT message via theRF interface; and resetting a register associated with the RF interfaceto indicate that the RF interface is not busy.